Method for increasing the oral bioactivity of pharmaceutical agents

ABSTRACT

A method of increasing the bioavailability upon oral administration of a pharmacologically active target agent, particularly an antitumor or antineoplastic agent which exhibits poor or inconsistent oral bioavailability (e.g., paclitaxel or etoposide), comprises the oral co-administration to a mammalian patient of the target agent and an oral bioavailability-enhancing agent, (e.g., cyclosporin A, cyclosporin D, ketoconazole or captopril). The enhancing agent may be administered orally from 0.5-24 hrs. prior to the oral administration of one or more doses of the target agent, substantially simultaneously with the target agent or both prior to and substantially simultaneously with the target agent. A method of treating mammalian patients suffering from diseases responsive to target agents with poor oral bioavailability, as well as oral dosage forms containing such target agents, combination oral dosage forms containing bioavailability-enhancing agents and target agents and kits containing enhancing and target agent dosage forms and dosing information for the co-administration of the same are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of provisional application Ser. No. 60/007,071, filed Oct. 26, 1995.

REFERENCE TO DISCLOSURE DOCUMENTS

This application incorporates material included in Disclosure Document No. 377063, filed Jun. 23, 1995, No. 386504, filed Dec. 11, 1995, No. 391109, filed Feb. 7, 1996 and No. 391228, filed Feb. 7, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to methods, compositions and kits for improving the oral bioavailability of pharmaceutical agents that are poorly absorbed from the gastrointestinal tract, and to methods of treatment of patients through the oral administration of such agents.

2. Description of the Prior Art

Many valuable pharmacologically active compounds cannot be effectively administered by the oral route because of poor systemic absorption from the gastrointestinal tract. All these pharmaceutical agents are, therefore, generally administered via intravenous or intramuscular routes, requiring intervention by a physician or other health care professional, entailing discomfort and potential local trauma to the patient and even requiring administration in a hospital setting in the case of certain IV infusions.

It has been speculated that, in some cases, the poor bioavailability of a drug after oral administration is a result of the activity of a multidrug transporter, a membrane-bound P-glycoprotein, which functions as an energy-dependent transport or efflux pump to decrease intracellular accumulation of drug by extruding xenobiotics from the cell. This P-glycoprotein has been identified in normal tissues of secretory endothelium, such as the biliary lining, brush border of the proximal tubule in the kidney and luminal surface of the intestine, and vascular endothelial cells lining the blood brain barrier, placenta and testis.

The P-glycoprotein efflux pump prevents certain pharmaceutical compounds from transversing the mucosal cells of the small intestine and, therefore, from being absorbed into the systemic circulation. A number of known non-cytotoxic pharmacological agents have been shown to inhibit P-glycoprotein, including cyclosporin A (also known as cyclosporine), verapamil, tamoxifen, quinidine and phenothiazines, among others. In fact, clinical trials have been conducted to study the effects of cyclosporine on the pharmacokinetics and toxicities of paclitaxel (Fisher et al., Proc. Am. Soc. Clin. Oncol., 13: 143,1994); doxorubicin (Bartlett et al., J. Clin. Onc. 12:835-842, 1994); and etoposide (Lum et al., J. Clin. Onc. 10:1635-42, 1992), all of which are anti-cancer agents known to be subject to multidrug resistance (MDR). These trials showed that patients receiving cyclosporine prior to or together with the anti-cancer drugs had higher blood levels of those drugs, presumably through reduced body clearance, and exhibited the expected toxicity at substantially lower dosage levels. These findings tended to indicate that the concomitant administration of cyclosporine suppressed the MDR action of P-glycoprotein, enabling larger intracellular accumulations of the therapeutic agents. For a general discussion of the pharmacologic implications for the clinical use of P-glycoprotein inhibitors, see Lum et al., Drug Resist. Clin. Onc. Hemat., 9: 319-336 (1995); Schinkel et al., Eur. J. Cancer, 31A: 1295-1298 (1995).

In the aforedescribed studies relating to the use of cyclosporine to increase the blood levels of pharmaceutical agents subject to P-glycoprotein mediated resistance, the active agents and the cyclosporine were administered intravenously. No suggestion was made in these publications that cyclosporine or other substances believed to inhibit the P-glycoprotein efflux pump could be orally administered to substantially increase the bioavailability of orally administered anti-cancer drugs and other pharmaceutical agents which are poorly absorbed from the gut without producing highly toxic side effects. Indeed, in the 1995 review paper cited above, Lum et al. showed that concomitant IV administration of MDR inhibitors and chemotherapeutic agents subject to MDR increased toxicity levels and exacerbated the patients' serious side effects. Schinkel et al. briefly adverted to the fact that MDR1 and P-glycoprotein are abundant in the mucosal cells of the intestine, and that this may affect the oral bioavailability of P-glycoprotein substrate drugs, but did not suggest or imply that the oral administration of MDR suppressing agents could improve the bioavailability of the orally unavailable agents. Furthermore, like Lum et al., Schinkel et al. warned that P-glycoprotein inhibitors can dramatically increase toxicity in chemotherapy patients and should, therefore, be used cautiously.

In an earlier publication, Schinkel et al. showed that absorption of orally ingested ivermectin was increased in mice homozygous for a disruption of the MDR1a gene in comparison with normal mice, demonstrating that P-glycoprotein played a major role in reducing the bioavailability of this agent (Cell, 77: 491-502, 1994). In addition, this study also showed that the penetration of vinblastine into various tissues was enhanced in the mutant mice.

None of the published studies provided any regimen for implementing the effective oral administration of poorly bioavailable drugs, e.g., indicating the respective dosage ranges and timing of administration for specific target drugs and bioavailability-enhancing agents or demonstrating which MDR-inhibiting agents are best suited for promoting oral absorption of each target drug or class of drugs.

Methods disclosed in the art for increasing gut absorption of drugs that have until now only been administered parenterally generally focus on the use of permeation and solubility enhancers as promoting agents, or the co-administration by intraluminal perfusion in the small intestine or by the intravenous route of P-glycoprotein inhibitors, e.g., Leu et al., Cancer Chemother. Pharmacol., 35: 432-436, 1995 (perfusion or IV infusion of quinidine suppresses efflux of etoposide into the lumen of the g.i. tract and/or may increase its oral bioavailability). But these methods suffer from numerous drawbacks. The solubility and permeability enhancing agents are often either impractical or ineffective for oral administration in the doses required and may interfere with the pharmacological activity of the target drug. Parenteral administration of P-glycoprotein inhibitors in therapeutic (or near-therapeutic) doses into humans can cause severe clinical consequences. In the case of quinidine, for example, IV administration may cause arrhythmias, peripheral vasodilation, gastrointestinal upset and the like.

A safe yet effective method for increasing the systemic availability upon oral administration of drugs that are currently administered only parenterally because they are not absorbed sufficiently or consistently when administered alone by the oral route, would be extremely valuable and desirable.

SUMMARY OF THE INVENTION

Surprisingly, it has now been discovered and experimentally verified that certain agents which apparently inhibit P-glycoprotein drug transport activity, particularly cyclosporins, can be used to increase substantially the oral bioavailability of otherwise poorly available or non-available pharmaceutical agents, e.g., the anti-cancer drugs paclitaxel (formerly known as taxol), as well as its analogs and derivatives, and etoposide.

The present invention relates in one aspect to a method of increasing the oral bioavailability of pharmaceutical agents that are poorly absorbed or not absorbed at all from the gastrointestinal tract or gut by pre-administering and/or simultaneously administering to a subject by the oral route one or a combination of agents known to be effective in inhibiting the P-glycoprotein drug transport pump. If pre-administration is used, the bioavailability enhancing agent or agents must be administered in sufficient quantities and within a short enough time period before administration of the drug whose bioavailability is to be increased (the "target drug" or "target agent") so that a sufficient level of the enhancing agent remains at the site of absorption at the time of administration of the target agent to effectively inhibit the activity of the P-glycoprotein or other multi-drug transporter substances.

In a second aspect, the invention pertains to compositions or dosage forms for oral administration of pharmaceutical agents that were heretofore available for parenteral administration only. A third aspect of the invention relates to the administration of such oral dosage forms or a combination thereof to patients for treatment of diseases responsive to the active agents contained therein.

The invention also pertains to pharmaceutical kits comprising one or more oral dosage forms containing a target agent and one or more oral dosage forms containing an enhancing agent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph reflecting the levels of paclitaxel in serum samples taken over a period of 6-8 hours from three groups of rats: one group administered only paclitaxel by intravenous administration, a second group administered only oral paclitaxel and a third group administered oral paclitaxel with oral cyclosporin A (hereinafter referred to as cyclosporine or CsA) doses prior to and together with the paclitaxel dose.

FIG. 2 is a graph comparing the levels of paclitaxel in serum taken from two of the three groups of rats reflected in FIG. 1: the group administered oral paclitaxel alone and the group administered oral paclitaxel with prior and concomitant doses of oral cyclosporine.

FIG. 3 is a graph reflecting the levels of paclitaxel in plasma samples taken over a period of 24 hours from two groups of rats: one group (A) administered cyclosporine orally one hour prior to the combination of cyclosporine plus oral paclitaxel and the second group (F) administered oral cyclosporine alone one hour prior to oral paclitaxel.

FIG. 4 is a graph reflecting the levels of paclitaxel in plasma samples from two groups of rats: one group (G) administered paclitaxel IV 3 hours after an oral dose of cyclosporine and the second group (H) administered only paclitaxel IV.

FIG. 5 is a graph reflecting the levels of radioactivity detected in whole blood samples taken from three groups of rats over a period of 24 hours: one (Group A) administered only radiolabeled paclitaxel IV, a second (Group B) administered only radiolabeled paclitaxel orally and a third group (Group C) administered radiolabeled paclitaxel orally with oral cyclosporine doses prior to and together with the paclitaxel dose.

FIG. 6 is a graph reflecting the levels of radioactivity detected in whole blood samples taken from the individual rats in Group B (defined with respect to FIG. 5).

FIG. 7 is a graph reflecting the levels of radioactivity detected in whole blood samples taken from the individual rats in Group C (defined with respect to FIG. 5).

FIG. 8 is a graph reflecting the levels of radioactivity detected in whole blood samples taken from three groups of rats over a period of 24 hours: one group administered 10 mg/kg of verapamil orally as an enhancing agent, a second administered progesterone orally as an enhancing agent and a third administered dipyridamole orally as an enhancing agent, with each group being administered an oral dose of the same enhancing agent one hour later together with an oral dose of radiolabeled paclitaxel.

FIG. 9 is a graph reflecting the levels of radioactivity detected in whole blood samples taken over a period of 24 hours from the rats of the first group defined with respect to FIG. 8 (administered 10 mg/kg verapamil orally), a group of rats administered oral radiolabeled paclitaxel alone and a group of rats administered cyclosporine orally one hour prior to and again together with radiolabeled oral paclitaxel.

FIG. 10 is a graph reflecting the levels of radioactivity detected in whole blood samples taken over a period of 24 hours from the rats of the second group defined with respect to FIG. 8 (administered progesterone orally), a group of rats administered radiolabeled oral paclitaxel alone and a group of rats administered cyclosporine orally one hour prior to and again together with radiolabeled oral paclitaxel.

FIG. 11 is a graph reflecting the levels of radioactivity detected in whole blood samples taken over a period of 24 hours from the rats of the third group defined with respect to FIG. 8 (administered dipyridamole orally), a group of rats administered radiolabeled oral paclitaxel alone and a group of rats receiving cyclosporine orally one hour prior to and again together with radiolabeled oral paclitaxel.

FIG. 12 is a graph reflecting the levels of radioactivity detected in whole blood samples taken from three groups of rats over a period of 24 hours: one group administered 100 mg/kg of verapamil orally¹ as an enhancing agent, a second administered megestrol acetate (marketed as MEGACE® by Bristol-Myers Squibb Oncology) orally as an enhancing agent and a third administered ketoconazole orally as an enhancing agent, with each group being administered the same oral dose of the same enhancing agent one hour later together with an oral dose of radiolabeled paclitaxel.

FIG. 13 is a graph reflecting the levels of radioactivity detected in whole blood samples taken over a period of 24 hours from the rats of the first group defined with respect to FIG. 12 (administered 100 mg/kg verapamil orally), a group of rats administered radiolabeled oral paclitaxel alone and a group of rats administered cyclosporine orally one hour prior to and again together with radiolabeled oral paclitaxel.

FIG. 14 is a graph reflecting the levels of radioactivity detected in whole blood samples taken over a period of 24 hours from the rats of the second group defined with respect to FIG. 12 (administered megestrol acetate orally), a group of rats administered radiolabeled oral paclitaxel alone and a group of rats administered cyclosporine orally one hour prior to and again together with radiolabeled oral paclitaxel.

FIG. 15 is a graph reflecting the levels of radioactivity detected in whole blood samples taken over a period of 24 hours from the rats of the third group defined with respect to FIG. 12 (administered ketoconazole orally), a group of rats administered radiolabeled oral paclitaxel alone and a group of rats receiving cyclosporine orally one hour prior to and again together with radiolabeled oral paclitaxel.

FIG. 16 is a graph reflecting the levels of radioactivity detected in whole blood samples taken over a period of 24 hours from the rats of the first group defined with respect to FIG. 8 (administered 10 mg/kg of verapamil), the first group defined with respect to FIG. 12 (administered 100 mg/kg of verapamil), a group of rats receiving radiolabeled oral paclitaxel alone and a group of rats receiving cyclosporine orally one hour prior to and again together with radiolabeled oral paclitaxel.

FIG. 17 is a graph reflecting the levels of radioactivity detected in whole blood samples taken over a period of 24 hours from the rats of the second group defined with respect to FIG. 8 (administered progesterone orally), the second group defined with respect to FIG. 12 (administered megestrol acetate orally), a group of rats receiving radiolabeled oral paclitaxel alone and a group of rats receiving cyclosporine orally one hour prior to and again together with radiolabeled oral paclitaxel.

FIG. 18 is a graph reflecting the levels of radioactivity detected in whole blood samples taken from three groups of rats over a period of 24 hours: one group administered only radiolabeled etoposide IV, a second administered only radiolabeled etoposide orally and a third administered radiolabeled etoposide orally with oral cyclosporine doses prior to and together with the etoposide dose, with the ordinate scale running from 0 to 1 whole blood ppm etoposide equivalents.

FIG. 19 is a graph reflecting the levels of radioactivity detected in whole blood samples taken from the three groups of rats defined in FIG. 18, with the ordinate scale running from 0 to 0.2 whole blood ppm radiolabeled etoposide equivalents.

FIG. 20 is a graph reflecting the mean cumulative % of dose of radioactivity detected in the feces and urine of three groups of rats over a period of 168 hours: one group administered only radiolabeled paclitaxel IV, a second administered only radiolabeled paclitaxel orally and a third administered radiolabeled paclitaxel orally with oral cyclosporine doses prior to and together with the paclitaxel dose.

FIG. 21 is a bar graph reflecting the mean ppm values of paclitaxel equivalents detected in blood and plasma from the three groups of rats defined in FIG. 20 168 hours (7 days) after administration of paclitaxel.

FIG. 22 is a bar graph reflecting the mean ppm values of paclitaxel equivalents detected in various tissues (liver, kidney, testes and carcass) from the three groups of rats defined in FIG. 20 168 hours (7 days) after administration of paclitaxel.

FIG. 23 is a bar graph reflecting the mean ppm values of paclitaxel equivalents detected in various tissues (muscle, pancreas, bone, lung and seminal vesicles) from the three groups of rats defined in FIG. 20 168 hours (7 days) after administration of paclitaxel.

FIG. 24 is a bar graph reflecting the mean ppm values of paclitaxel equivalents detected in various tissues (brain, heart, G.I. tract, spleen and prostate) from the three groups of rats defined in FIG. 20 168 hours (7 days) after administration of paclitaxel.

FIG. 25 is a graph reflecting the levels of radioactivity detected in whole blood samples taken from three groups of rats over a period of 24 hours: one group administered cyclosporin D orally both one hour before and together with an oral dose of radiolabeled paclitaxel, a second group administered cyclosporin G orally both one hour before and together with an oral dose of radiolabeled paclitaxel, and a third group administered cyclosporin A both one hour before and together with an oral dose of radiolabeled paclitaxel.

FIG. 26 is a graph reflecting the levels of radioactivity detected in whole blood samples taken from three groups of rats over a period of 24 hours: one group administered ketoconazole orally both one hour before and together with an oral dose of radiolabeled paclitaxel, a second group administered a combined oral dose of cyclosporin A and ketoconazole both one hour before and together with an oral dose of radiolabeled paclitaxel, and a third group administered cyclosporin A both one hour before and together with an oral dose of radiolabeled paclitaxel.

FIG. 27 is a graph reflecting the levels of radioactivity detected in whole blood samples taken from three groups of rats over a period of 24 hours: one group administered captopril orally both two hours before and together with an oral dose of radiolabeled paclitaxel, a second group administered cyclosporin A both one hour before and together with an oral dose of radiolabeled paclitaxel and a third group administered orally radiolabeled paclitaxel alone.

FIG. 28 shows the radioactivity profile from an HPLC-plasma extract from the rats in Group C defined with respect to FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

The present invention pertains generally to increasing the oral absorption and bioavailability upon oral administration of pharmacologically active agents, particularly agents that are poorly absorbed or not absorbed at all from the gastrointestinal tract or gut. The preferred embodiments of the invention pertain to (a) a method for increasing the oral bioavailability of antitumor agents, in particular paclitaxel and its derivatives, other taxanes, the semi-synthetic paclitaxel analog docetaxel (N-debenzoyl-N-tert-butoxycarbonyl-10-deacetyl paclitaxel), produced under the trademark TAXOTERE® by Rhone-Poulenc Rorer S.A., and etoposide; (b) dosage forms and kits for oral administration of antitumor agents and other drugs heretofore administered only parenterally; and (c) methods of treatment of cancer patients with such oral dosage forms or combinations thereof.

The phrases "oral bioavailability" and "bioavailability upon oral administration" as used herein refer to the physiological availability of a given amount of drug administered orally to a patient.

Paclitaxel is a natural diterpene product isolated from the Pacific yew tree (Taxus brevifolia). It is a member of the taxane family of terpenes. It was first isolated in 1971 by Wani et al. (J. Am. Chem. Soc., 93:2325, 1971), who characterized its structure by chemical and X-ray crystallographic methods.

Paclitaxel has been approved for clinical use in the treatment of refractory ovarian cancer in the United States (Markman et al., Yale Journal of Biology and Medicine, 64:583, 1991; McGuire et al., Ann. Intern. Med., 111:273, 1989). It is effective for chemotherapy for several types of neoplasms including breast (Holmes et al., J. Nat. Cancer Inst., 83:1797, 1991) and has been approved for treatment of breast cancer as well. It is a potential candidate for treatment of neoplasms in the skin (Einzig et al., Proc. Am. Soc. Clin. Oncol., 20:46) and head and neck carcinomas (Forastire et al. Sem. Oncol., 20:56, 1990). The compound also shows potential for the treatment of polycystic kidney disease (Woo et al., Nature, 368:750, 1994), lung cancer and malaria.

Paclitaxel is only slightly soluble in water and this has created significant problems in developing suitable injectable and infusion formulations useful for anticancer chemotherapy. Some formulations of paclitaxel for IV infusion have been developed utilizing CREMOPHOR EL™ (polyethoxylated castor oil) as the drug carrier because of paclitaxel's aqueous insolubility. For example, paclitaxel used in clinical testing under the aegis of the NCI has been formulated in 50% CREMOPHOR EL™ and 50% dehydrated alcohol. CREMOPHOR EL™ however, when administered intravenously, is itself toxic and produces vasodilation, labored breathing, lethargy, hypotension and death in dogs. It is also believed to be responsible for the allergic-type reactions observed during paclitaxel administration.

In an attempt to increase paclitaxel's solubility and to develop more safe clinical formulations, studies have been directed to synthesizing paclitaxel analogs where the 2' and/or 7-position is derivatized with groups that would enhance water solubility. These efforts have yielded prodrug compounds that are more water soluble than the parent compound and that display the cytotoxic properties upon activation. One important group of such prodrugs includes the 2'-onium salts of paclitaxel and docetaxel, particularly the 2'-methylpyridinium acetate (2'-MPA) salts.

Paclitaxel is very poorly absorbed when administered orally (less than 1%) and no effective method has been developed to enable the effective administration of oral paclitaxel (i.e., a method of increasing the oral bioavailability of paclitaxel) or of other oral taxanes or paclitaxel analogs such as taxotere which exhibit antitumor activity. For this reason, paclitaxel has not until now been administered orally to human patients, and certainly not in the course of treating paclitaxel-responsive diseases.

Etoposide is a semisynthetic derivative of podophyllotoxin and is used in the treatment of certain neoplastic diseases, particularly germ cell cancers (e.g., testicular cancers) and small cell lung cancers (Loehrer, Sem. Onc., 19, no. 6, supp. 14, pp. 48-52, 1992). It is available in oral dosage form (VEPESID® capsules, Bristol-Myers Squibb Oncology) but is not consistently well-absorbed orally (the mean value of oral bioavailability for etoposide capsules is approximately 50%).

Cyclosporins are a group of nonpolar cyclic oligopeptides (some of which have immunosuppressant activity) produced by the genus Topycladium, including, e.g. Topycladium inflatum Gams (formerly designated as Trichoderma polysporum) Topycladium terricola, and other fungi imperfecti. The major component, cyclosporin A (cyclosporine or CsA), has been identified along with several other lesser metabolites, for example, cyclosporins B through Z, some of which exhibit substantially less immunosuppressive activity than cyclosporin A. A number of synthetic analogs have also been prepared. See generally Jegorov et al., Phytochemistry, 38: 403-407 (1995).

Cyclosporins are neutral, lipophilic, cyclic undecapeptides with molecular weights of about 1200. They are used intravenously or orally as an immunosuppressant, primarily for organ transplantation and certain other conditions. Cyclosporins, particularly cyclosporine, are known inhibitors of the P-glycoprotein efflux pump, but to date no effective regimen for applying this property clinically has been developed to the point of clinical and commercial feasibility or regulatory approval.

From a mechanistic point of view, orally administered cyclosporine has the potential to inhibit the P-glycoprotein pump in the upper small intestine which is the site at which most drugs are absorbed. With intravenous administration of a drug which is highly metabolized like cyclosporine, it is not possible for it to appear intact in that region of the gut where drugs are normally absorbed. After parenteral administration, cyclosporine is extracted by the liver and enters the bile and gut distal to this area of optimal absorption. One of the surprising discoveries of the invention is that the immunosuppression observed with certain cyclosporins is not inextricably linked to improvement in oral bioavailability of therapeutic agents.

Ketoconazole is a widely used antifungal imidazole derivative which has also been used to some extent in the treatment of prostate carcinoma. Ketoconazole has been shown, as one of its activities, to reverse MDR in highly resistant human KB carcinoma cells (Siegsmund et al., J. Urology, 151: 485-491, 1994), but also can inhibit the cytochrome P-450 drug-metabolizing enzymes.

It has now been discovered that many pharmaceutical agents with poor oral absorption profiles can be effectively administered orally with sufficient systemic absorption to exhibit therapeutic activity levels when said agents are co-administered orally with an oral dose of cyclosporins or other agents known to inhibit the multidrug resistance, drug transport activity of the P-glycoprotein intracellular pump. A further surprising discovery of our invention is that under some conditions, the oral administration leads to a more favorable pharmacokinetic profile and better tissue penetration of the target therapeutic agent.

We have observed in animal studies that certain multidrug resistance suppressing agents such as cyclosporine and ketoconazole, when administered orally together with and/or before drugs such as paclitaxel and etoposide, increase absorption of the latter drugs from the gut to an unexpected and surprising degree. It is not at all clear, however, that these observed results are due to the suppression of the P-glycoprotein pump.

Another possible explanation for the observed increased bioavailability of paclitaxel and etoposide is that there may be interaction at the level of the drug metabolizing enzymes for cyclosporine and paclitaxel. It is known that both agents are highly metabolized by the cytochrome P-450 system (e.g., P-450 3A), which is concentrated in the liver as well as the small intestine. It is conceivable that cyclosporine which was administered first may have inhibited these enzymes so that paclitaxel, which is non-polar and lipophilic, could be absorbed. In the absence of this local inhibition, paclitaxel would be metabolized to more polar metabolites which would not transverse the mucosal cells. The failure to demonstrate a pharmacokinetic interaction between cyclosporin and paclitaxel when cyclosporin was given 3 hr prior to administration of IV paclitaxel suggests that the site of interaction was the gut lumen. Even this theoretical explanation does not account for our surprising discovery that certain P-glycoprotein inhibitors (e.g., cyclosporins and ketoconazole) increase oral bioavailability of specific target drugs to a high degree, whereas other agents known to be active P-glycoprotein inhibitors exhibit little activity as oral absorption enhancers for the same target drugs.

This theorized inhibition of gut metabolism of the target agent would have little or no effect in increasing systemic blood levels when the target agent is administered intravenously. Moreover, since the primary effect of the oral absorption enhancing agent may be a local effect in the gut lumen, subtherapeutic doses should be effective in achieving the desired effect. This is an important consideration in the case of enhancing agents such as cyclosporins which have powerful immunosuppressant activity and can present toxicity problems if administered at high dose levels.

It is important to note that while we provide hypotheses as to the mechanisms of action which underlie our invention, we do not actually know the mechanism(s) responsible for the surprising findings discussed herein; and this does not impede one of skill in the art from practicing the invention described.

The method of the invention for increasing the oral bioavailability of a target therapeutic agent with poor oral bioavailability (average or mean bioavailability 50% or less) comprises the oral administration of an oral absorption or bioavailability enhancing agent to a mammalian patient (human or animal) simultaneously with, or prior to, or both simultaneously with and prior to the oral administration to increase the quantity and duration of absorption of the intact target agent into the bloodstream.

The class of orally administered enhancing agents which may be used in accordance with the invention includes, but is not limited to, the following:

Cyclosporins, including cyclosporins A through Z but particularly cyclosporin A (cyclosporine), cyclosporin G and cyclosporin D (which has considerably less immunosuppressive activity than A or G), PSC-833, SDZ-NIM 811² (both from Sandoz Pharmaceutical Corp.), and related oligopeptides produced by species in the genus Topycladium. The structures of cyclosporins A-Z are described in Table 1 below.

Antifungals--ketoconazole.

Cardiovascular drugs--verapamil, dexverapamil, MS-209 (from BASF) amiodarone, nifedipine, diltiazem, reserpine, quinidine, nicardipine, dipyridamole, captopril, ethacrynic acid, propafenone, reserpine, amiloride.

Phenothiazines--trifluoperazine, fluphenazine.

Anti-inflammatories--colchicine.

Anti-migraine natural products--ergot alkaloids

Antibiotics--quinine, cefoperazone, tetracycline,

chloroquine, fosfomycin.

Antiparasitics--ivermectin.

Hormones--tamoxifen, progesterone, megestrol acetate.

Multi-drug resistance reversers--VX-710 and VX-853 (Vertex Pharmaceutical Incorporated).

Tyrosine kinase inhibitors--genistein and related isoflavonoids, quercetin.

Protein kinase C inhibitors--calphostin.

Apoptosis inducers--ceramides. and

Agents active against endorphin receptors--morphine, morphine congeners, other opioids and opioid antagonists including (but not limited to) naloxone, naltrexone and nalmefene).

The class of orally administered target therapeutic agents whose oral absorption is increased by the enhancing agents includes, but is not limited to, the following:

Paclitaxel, other taxanes, docetaxel and derivatives and prodrugs of all of the foregoing, particularly their 2'-MPA salts and other 2'-methylpyridinium salts.

Other chemotherapeutic agents which have poor or highly variable oral bioavailability including etoposide, camptothecin, CPT-11 (Pharmacia and Upjohn), doxorubicin, vincristine, daunorubicin, mitoxantrone and colchicine, all of which are believed to be affected by the P-glycoprotein efflux.

Other drugs which have not been shown to be handled by P-glycoprotein but which can be made orally absorbable in the presence of an inhibitor of P-glycoprotein in the gut, including ganciclovir, foscarnet, camptothecin and camptothecin derivatives.

                                      TABLE 1                                      __________________________________________________________________________     Cyclosporins A-Z                                                               1 #STR1##                                                                      Cyclosporin                                                                          Aminoacids                                                               Cy-   1    2  3  4   5  6   7  8   9   10  11                                  __________________________________________________________________________     Cy A  Mebmt                                                                               Abu                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                               Cy B  Mebmt                                                                               Ala                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                               Cy C  Mebmt                                                                               Thr                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                               Cy D  Mebmt                                                                               Val                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                               Cy E  Mebmt                                                                               Abu                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              Val                                 Cy F  Desoxy-                                                                             Abu                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                                     Mebmt                                                                    Cy G  Mebmt                                                                               Nva                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                               Cy H  Mebmt                                                                               Abu                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              D-Mev                               Cy I  Mebmt                                                                               Val                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              Leu MeVal                               Cy K  Desoxy-                                                                             Val                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                                     Mebmt                                                                    Cy L  Bmt  Abu                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                               Cy M  Mebmt                                                                               Nva                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                               Cy N  Mebmt                                                                               Nva                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              Leu MeVal                               Cy O  MeLeu                                                                               Nva                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                               Cy P  Bmt  Thr                                                                               Sar                                                                               MeLeu                                                                              Val                             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                                                                    Sar                                                                               MeLeu                                                                              Val                                                                               Leu Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                               Cy Z  MeAmino                                                                             Abu                                                                               Sar                                                                               MeLeu                                                                              Val                                                                               MeLeu                                                                              Ala                                                                               D-Ala                                                                              MeLeu                                                                              MeLeu                                                                              MeVal                                     octylacid                                                                __________________________________________________________________________

The dosage range of the enhancing agent to be co-administered with the target agent in accordance with the invention is about 0.1 to about 15 mg/kg of patient body weight. "Co-administration" of the enhancing agent comprehends administration substantially simultaneously with the target agent (either less than 0.5 hr. before, less than 0.5 hr. after or together), from about 0.5 to about 24 hr. before the administration of the target agent, or both, i.e., with one or more doses of the same or different enhancing agents given at least 0.5 hr. before and one dose given substantially simultaneously with the target agent. Additionally, "co-administration" comprehends administering more than one dose of target agent within 24 hrs after a dose of enhancing agent, in other words, the enhancing agent(s) need not be administered again before or with every administration of target agent, but may be administered intermittently during the course of treatment.

The dosage range of orally administered target agents will vary from drug to drug based on its therapeutic index, the requirements of the condition being treated, the status of the subject and so forth. The method of the invention makes it possible to administer paclitaxel orally ranging from about 20 mg/m² to about 600 mg/m² (based on patient body surface area) or about 2-9 mg/kg (based on patient body weight) as single or divided (2-3) daily doses, and maintain the plasma levels of paclitaxel in humans in the range of 50-500 ng/ml for extended periods of time (e.g., 8-12 hours) after each oral dose. These levels are at least comparable to those achieved with 96-hour IV infusion taxol therapy (which causes the patient great inconvenience, discomfort, loss of time, infection potential, etc.). Moreover, such plasma levels of paclitaxel are more than sufficient to provide the desired pharmacological activities of the target drug, e.g., inhibition of tubulin disassembly (which occurs at levels of about 0.1 μM, or about 85 ng/ml) and inhibition of protein isoprenylation (which occurs at levels of about 0.03 μM, or about 25 ng/ml) which are directly related to its antitumor effects by inhibiting oncogene functions and other signal-transducing proteins that play a pivotal role in cell growth regulation.

It may be suitable in some instances to administer to the subject a higher initial loading dose of the target agent to achieve peak blood levels, followed by lower maintenance doses.

Two or more different enhancing agents and/or two or more different target agents may be administered together, alternately or intermittently in all of the various aspects of the method of the invention.

The present invention also comprehends methods of treating mammalian patients afflicted with cancers, tumors, malignancies and all other disease conditions responsive to paclitaxel, taxanes, docetaxel, etoposide, prodrugs and derivatives of all the foregoing, paclitaxel 2'-MPA, and docetaxel 2'-MPA with orally administered dosage forms comprising one or more of those agents. Among the types of carcinoma which may be treated effectively with oral paclitaxel, docetaxel, other taxanes, and their prodrugs and derivatives, are hepatocellular carcinoma and liver metastases. Examples of non-cancerous disease conditions which may be effectively treated with these active agents administered orally in accordance with the present invention are polycystic kidney disease and malaria, including chloroquine- and pyrimethamine-resistant malaria parasites (Pouvelle et al., J. Clin. Invest., 44: 413-417, 1994).

The antitumor agents which heretofore were administered only parenterally can now be administered in accordance with the invention by the oral route with sufficient bioavailability to provide pharmacologically active blood concentrations which will be particularly effective in the treatment of patients with primary tumors and metastases. The active ingredients will penetrate the gut wall as a result of the prior and/or concomitant administration of the MDR inhibitors and will be taken up by the portal circulation rapidly, providing a higher local initial concentration of the chemotherapeutic agents in the liver (a far higher local concentration than is currently achieved with IV infusion therapy) than in the general systemic circulation or in other organs. Furthermore, it should be noted that the higher levels of paclitaxel in the liver after oral administration may not be reflected in increased plasma levels because of the high first pass effect of the liver. The method of the invention, in selectively producing high blood concentrations of antitumor agents, is particularly valuable in the treatment of liver cancers, including, e.g., hepatocellular carcinoma and liver metastases.

FIGS. 21-24 are especially noteworthy. Our invention, in certain cases, provides a method for achieving comparable and sometimes higher local tissue concentrations of paclitaxel via the oral route than the intravenous route. Furthermore, oral administration of an enhancing agent before and together with a target agent has been shown (in the case of cyclosporine and paclitaxel, see FIG. 20) to produce a higher concentration of the target agent in the urine than even IV administration. This should make the oral co-administration of enhancing agent with target agent a treatment of choice in the case of patients with tumors or metastases in the genito-urinary tract.

Apart from the higher than previously achieved local concentration of the active ingredients in the liver, the plasma and tissue distribution of the active target agents administered orally with the appropriate enhancing agents as provided in the present invention is remarkably and surprisingly similar to that observed upon IV administration. Moreover, and quite significantly, the elimination-phase concentration in the blood of paclitaxel and the other antitumor agents listed above, when administered orally as provided herein, is approximately equal to that achieved with IV administration, and these high, therapeutically effective levels, can be maintained in a fairly steady state for as long as 8-12 hours after each administration. The increase in excretion of drug after oral administration in the presence of CsA not only supports the enhanced oral absorption of paclitaxel but also provides more drug being delivered to the genito-urinary tract for the treatment of cancers.

Oral dosage forms of the target agents whose bioavailability is increased by the co-administration of the enhancing agents may be in the form of conventional tablets, capsules, caplets, gelcaps, pills, liquids (e.g., solutions, suspensions or elixirs), lozenges and any other oral dosage forms known in the pharmaceutical arts. The liquid preparations may include, for example, paclitaxel in a vehicle comprising CREMOPHOR EL or other polyethoxylated castor oil. Each dosage form includes an effective amount of a target agent (for example, effective antitumor or antineoplastic amounts of an antitumor or antineoplastic agent) and pharmaceutically inert ingredients, e.g., conventional excipients, vehicles, fillers, binders, disentegrants, solvents, solubilizing agents, sweeteners, coloring agents and any other inactive ingredients which are regularly included in pharmaceutical dosage forms for oral administration. Many such dosage forms and oral vehicles together with listings of inactive ingredients therefor are set forth in Remington's Pharmaceutical Sciences, 17th edition (1985). Each dosage form also contains a pharmacologically effective amount, for example, an effective antineoplastic or tumor-reducing amount, of one of the target drugs.

Precise amounts of each of the target drugs in the oral dosage forms will vary depending on the age, weight, disease and condition of the patient. For example, paclitaxel dosage forms may contain sufficient quantities of paclitaxel to provide a daily dosage of about 20-600 mg/m² (based on patient body surface area) or about 2-9 mg/kg (based on patient body weight) as single or divided (2-3) daily doses. Etoposide oral dosage forms may contain sufficient quantities of etoposide to provide a daily dosage of about 20-200 mg/m² (based on average or median patient body surface area) as single or divided (2-3) daily doses.

As already indicated, certain of the target agents are commercially available in oral dosage forms, despite their relatively poor or inconsistent oral bioavailability. For example, VEPESID® capsules are available containing 50 mg each of etoposide.

In establishing a treatment regimen for a particular patient treated with the oral, target drug-containing dosage forms of the invention, it is necessary to take into account the increased bioavailability provided by the concomitant and/or prior oral administration of the enhancing agents. For example, although the manufacturerrecommended dosage amount of VEPESID® capsules in the treatment of small cell lung cancer is two times the IV dose rounded to the nearest 50 mg, the increased bioavailability of etoposide provided by pre-and/or substantially simultaneous administration of enhancing agents such as cyclosporins, allows a considerably lower dosage of oral etoposide to be used to provide the same effective blood levels of the drug, with greater duration and stability of action and no increase (and perhaps a decrease) in toxic side effects. With oral administration one can avoid the high peak blood levels which are responsible for some of the toxicities. Based on our experimental data (see FIGS. 18 and 19 and Table 6), which indicate that the oral absorption of etoposide is essentially complete (about 96%) in the presence of cyclosporine, the oral daily dosage range for etoposide in the treatment of testicular cancer should be about 50-100 mg/m² and in the treatment of small cell lung cancer about 35-50 mg/m², based on patient body surface area.

Dosing schedules for the treatment method of the present invention, for example, the treatment of paclitaxel-responsive diseases with oral paclitaxel dosage forms co-administered with enhancing agents, can likewise be adjusted to account for the patient's characteristics and disease status. Preferred dosing schedules for administration of oral paclitaxel are (a) the daily administration to a patient in need thereof of 1-3 equally divided doses providing about 20-600 mg/m² (based on body surface area), with said daily administration being continued for 1-4 consecutive days each 2-3 weeks, or (b) administration for about one day each week. The former schedule is comparable to use of a 96-hour paclitaxel infusion every 2-3 weeks, which is considered by some a preferred IV treatment regimen. A preferred dosing schedule for oral administration of etoposide co-administered with enhancing agents is the daily administration to a patient in need thereof of 1-3 equally divided doses providing about 50-100 mg/m² (based on body surface area) in the treatment of patients with testicular cancer and about 35-50 mg/m² as a daily dose in the treatment of small cell lung cancer, with the daily administration being continued for 5-21 days in each case and with a period of about 2-3 weeks in between each course of treatment.

Oral administration of powerful chemotherapeutic agents in accordance with the invention may actually decrease toxic side effects in many cases as compared with currently utilized IV therapy. Rather than producing a sudden and rapid high concentration in blood levels as is usually the case with an IV infusion, absorption of the active agent through the gut wall (promoted by the enhancing agents), provides a more gradual appearance in the blood levels and a stable, steady-state maintenance of those levels at or close to the ideal range for a long period of time.

Pursuant to another aspect of the invention, combination oral dosage forms are provided which contain fixed quantities of at least one enhancing agent and at least one target agent. For example, such dosage forms can consist of tablets, capsules, caplets, gelcaps, pills, liquids, lozenges and any other conventional oral dosage forms containing as active ingredients an effective oral bioavailability enhancing amount of an antitumor or anti-neoplastic agent, as well as suitable inactive ingredients. One such combination product includes from about 0.1 to about 15 mg/kg of cyclosporine or cyclosporin D together with about 20 to about 600 mg/m² (based on average patient body surface area) of paclitaxel, docetaxel, other taxanes or paclitaxel or docetaxel derivatives such as paclitaxel 2'--MPA or docetaxel 2'--MPA. Another such dosage form includes about 0.1 to about 15 mg/kg of cyclosporine or cyclosporin D together with about 20 mg/m² to 200 mg/m² of etoposide.

The co-administration of enhancing agents with the target drugs promotes not only the oral bioavailability of those agents but also enables their use in the treatment of tumors at sites highly protected by MDR, e.g., the testes and the brain. Another aspect of the present invention is, thus, a method of delivering antitumor drugs to tumor sites protected by MDR through the oral co-administration of enhancing agents and the antitumor agents.

Yet another aspect of the present invention is a method of delivering an active paclitaxel metabolite to a disease site at therapeutic levels to treat paclitaxel-responsive diseases. The major in vivo metabolites of paclitaxel have been identified, particularly the following hydroxylated paclitaxel metabolites A, B and C: ##STR2##

In certain in vitro tests metabolite B shown above (also referred to in the literature as metabolite M4) has been found to have a higher therapeutic index (ratio of toxic concentration level to effective concentration level) than paclitaxel in some human tumor cell lines. The invention possibly enables delivery of enhanced amounts of metabolite B and other active metabolites of paclitaxel to tumor sites because upon oral administration all of the administered paclitaxel will pass through the liver and undergo metabolism by liver microsomes, yielding more of each metabolite in the systemic circulation than is achieved with IV administration.

An additional aspect of the invention relates to kits to be used in the treatment of mammalian patients suffering from conditions responsive to any pharmacologically active target agents whose oral absorption and bioavailability is increased by an enhancing agent. These kits include one or more oral dosage forms of at least one enhancing agent and one or more oral dosage forms of at least one target agent, or one or more dosage forms which comprise both.

By way of illustration, a kit of the invention may include one or more tablets, capsules, caplets, gelcaps or liquid formulations containing cyclosporine or ketoconazole, and one or more tablets, capsules, caplets, gelcaps or liquid formulations containing paclitaxel or etoposide in dosage amounts within the ranges described above. Such kits may be used in hospitals, clinics, physician's offices or in patients' homes to facilitate the co-administration of the enhancing and target agents. The kits should also include as an insert printed dosing information for the co-administration of the enhancing and target agents.

The subject kits may also include combinations of different enhancing agents and/or combinations of target agents. For example, a kit may include oral dosage forms respectively containing a cyclosporin and ketoconazole as enhancing agents, with paclitaxel alone as the target agent or with a combination of paclitaxel and another antitumor drug. The second target agent should be (like paclitaxel) a drug that exhibits poor oral bioavailability but with co-administration of enhancing agents can achieve therapeutically effective blood levels upon oral administration. The target agent may co-exist with the enhancing agent in the same dosage form or may be in a separate dosage form.

The following examples illustrate various aspects of the invention and demonstrate the unexpected, very substantial increases in the oral absorption of target agents achieved. These examples are not intended, however, to limit the invention in any way or to set forth specific enhancing or target agents, dosage ranges, testing procedures or other parameters which must be used exclusively to practice the invention.

EXAMPLE 1

Eighteen (18) healthy Sprague Dawley rats, all weighing from 225-275 grams and approximately six to eight weeks old, were randomly divided into three groups of six animals. The first group of six rats received a single IV administration of paclitaxel at a dose of 9 mg/kg. The second group received a single oral dose of paclitaxel at 9 mg/kg. The third group received a single oral dose of cyclosporine at 5 mg/kg, and one hour later the same group received an oral dose of 5 mg/kg cyclosporine and 9 mg/kg paclitaxel.

Blood samples were collected from the tail vein of each rat at 0.5, 1, 2, 3, 4 and 6 hours after the paclitaxel dose. In the case of the IV-treated rats of the first group, an additional blood sample was taken at eight hours after the paclitaxel dose. The individual samples were centrifuged and the serum was separated. For each time interval, the six samples per group were composited to produce a single representative sample. All samples were assayed for unchanged paclitaxel by LC/MS with a lower limit of quantitation of 50 pg/ml.

The results of the study are graphically illustrated in FIGS. 1 and 2. FIG. 1 compares all three groups of rats while FIG. 2 compares only the second and third groups which received oral paclitaxel. It may be seen that in the absence of cyclosporine, the bioavailability of the paclitaxel in serum was less than 1% but it rose to 6-7% in the third group which received cyclosporine one hour prior to a cyclosporine/paclitaxel combined dose.

The following Table 2 sets forth data regarding the area under the curve (AUC) values determined for the three groups of rats. These data indicate that the AUC value over six hours in the case of the third group of rats receiving both cyclosporine and paclitaxel was almost eight times the AUC for the second group of rats receiving only oral paclitaxel.

                  TABLE 2                                                          ______________________________________                                         Paclitaxel Absolute Bioavailability                                            AUC.sub.0-6hr IV                                                                         AUC.sub.0-6hr PO                                                     (ng. hr/mL)                                                                              (ng. hr/mL)       Absolute F                                         ______________________________________                                         9230*     80                0.9%                                               ______________________________________                                          *AUC value which does not include 1hr sample point                             **F = [AUC.sub.PO /AUC.sub.IV ] × 100                              

    Paclitaxel Interaction with Cyclosporin                                        AUC.sub.0-6hr PO                                                                         AUC.sub.0-6hr PO with Cyclosporin                                    (ng. hr/mL)                                                                              (ng. hr/mL)       Relative F***                                      ______________________________________                                         80        629               786%                                               ______________________________________                                          ***F = [AUC.sub.PO with Cyclosporin /AUC.sub.PO ] × 100            

EXAMPLE 2

Forty (40) healthy Sprague Dawley rats with the same characteristics as those used in the study described in Example 1 were randomly divided into four groups of ten each labeled Groups A, F, G and H. The following Table 3 indicates the treatment provided to each of the test groups and the time intervals for each dosage administration.

                  TABLE 3                                                          ______________________________________                                               No. of   Time            Dose   Route of                                 Group Rats     (Hour)  Treatment                                                                              (mg/kg)                                                                               Administration                           ______________________________________                                         A     10       0       cyclosporin                                                                            5      oral                                                    1       paclitaxel                                                                             9      oral                                                    1       cyclosporin                                                                            5      oral                                     F     10       0       cyclosporin                                                                            5      oral                                                    1       paclitaxel                                                                             9      oral                                     G     10       0       cyclosporin                                                                            5                                                              3       paclitaxel                                                                             9      IV                                       H     10       0       paclitaxel                                                                             9      IV                                       ______________________________________                                    

Blood samples were collected from the tail vein of each rat at 0.25, 0.5, 1, 2, 3, 4, 5, 6, 8, 12 and 24 hours after paclitaxel administration. After appropriate treatment of the samples and the creation of one composite sample for each group, the plasma from each sample was assayed for unchanged paclitaxel.

FIGS. 3 and 4 graphically illustrate the results of this study. In FIG. 3 a comparison is shown between the concentration levels achieved over time in Group A, which received a cyclosporine pre-dose and a combined paclitaxel-cyclosporine dose one hour later, and Group F, which received-a cyclosporine pre-dose and then only oral paclitaxel one hour later. FIG. 4 reflects a comparison between the results achieved with Groups G and H, both of which received paclitaxel IV but with Group G receiving a pre-dose of oral cyclosporine three hours before the paclitaxel. As indicated in FIG. 4, the two groups exhibited essentially the identical levels of paclitaxel in plasma at the same time intervals.

Table 4 sets forth the AUC data for the four groups of rats in this study. While the AUC values for Groups G and H were essentially the same, the AUC value for Group A was 25-30% higher than that for Group F, indicating the value of providing both cyclosporine pre-treatment and co-administration of cyclosporine with paclitaxel.

                  TABLE 4                                                          ______________________________________                                         Bioavailability of Paclitaxel in Plasma                                        Treatment           AUC.sub.O-t                                                                            F (%)                                              ______________________________________                                         IV (Group H)        24280                                                      IV + CsA Oral.sup.a (Group G)                                                                      24137   99.4                                               Oral + CsA* (Group F)                                                                              1097    4.5                                                Oral + CsA** (Group A)                                                                             1393    5.7                                                ______________________________________                                          .sup.a 3 hr prior to paclitaxel                                                *1 hr pretreatment with CsA                                                    **1 hr pretreatment and simultaneously with paclitaxel                   

EXAMPLE 3

Eighteen (18) healthy Sprague Dawley rats with the same characteristics as those used in the study described in Example 1 were randomly divided into three groups of six rats, Groups A, B and C. Group A was administered radiolabeled paclitaxel IV; Group B received 3H-radiolabeled paclitaxel orally; and Group C received an oral dose of cyclosporine followed one hour later by a combined oral dose of cyclosporine and radiolabeled oral paclitaxel.

Blood samples were collected from the tail veins of each rat at the same time intervals as described in Example 2. The samples were kept in the form of whole blood. In addition, urine samples were taken from each rat 4-24 hours post-paclitaxel dose. The blood and urine samples were analyzed for radioactivity.

A comparison of the paclitaxel levels in the whole blood samples from Groups A, B and C is set forth in FIG. 5. Comparisons of the levels for the individual members of Groups B and C are set forth in FIGS. 6 and 7, respectively.

In this study, the oral absorption of radioactivity (expressed as paclitaxel equivalency) in whole blood was 9.7% in the absence of cyclosporine (Group B) and 36% with concomitant cyclosporine administration (Group C). This was determined by measuring the AUC of blood radioactivity after intravenous and oral radiolabeled paclitaxel. The bioavailability of paclitaxel was not determined formally in this study because that would require assaying for unchanged drug at each time point. At one time point, though, the radioactivity was extracted from plasma and after standard HPLC it appeared that at least 32% of the radioactivity in the plasma was unchanged paclitaxel. The radioactivity profile from the HPLC-plasma extract of Group C animals, demonstrating predominantly one peak (which is paclitaxel), is shown in FIG. 28. Set forth below in Table 5 are AUC, C_(max), T_(max), and other data generated by this study.

                  TABLE 5                                                          ______________________________________                                         Total Radioactivity for Paclitaxel in Blood/Urine                              PK Parameter   IV (A)   PO (B)  PO + CsA** (C)                                 ______________________________________                                         AUC.sub.0-24 (μg eq × hr/ml)                                                         32.8     3.2     12.1                                           C.sub.max (μg eq/ml)                                                                       ND       0.21    0.82                                           T.sub.max (hr) --       2       5                                              % Dose in urine (4-24 hr)                                                                      2.2     1.9     8.3                                            % Paclitaxel*  ND       7.8***  32***                                          ______________________________________                                          *% as paclitaxel from extracted RA at 4hr sample.                              **CsA given 1 hr prior to and simultaneously with paclitaxel.                  ***These numbers are lower estimates based upon the incomplete extraction      procedure.                                                               

In Examples 4-5 the following study design was utilized: Sprague-Dawley rats with the same characteristics as those used in the study described in Example 1 were divided into three groups of three male rats each. All of the rats were fasted 12-14 hours prior to dosing. At the end of the fasting period, those rats receiving enhancing agents were administered those agents, and one hour later received a dose of radiolabeled (3H) paclitaxel (9 mg/kg) with concomitant doses of enhancing agent. The rats not receiving enhancing agents were administered the radiolabeled paclitaxel after fasting.

Blood was collected from each animal at 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 12 and 24 hours following the paclitaxel dosing. Urine was collected from 4-24 hours post dose. Total radioactivity in blood and urine was then determined for each rat and mean values were calculated for each group.

EXAMPLE 4

Three groups of rats were administered, respectively, 10 mg/kg of verapamil orally, 5 mg/kg of progesterone orally and 10 mg/kg of dipyridamole orally as enhancing agents, both alone and one hour later with an oral dose of paclitaxel. A graphical comparison of the whole blood concentration-time profile (measured as concentration equivalents versus time) determined for the three groups is set forth in FIG. 8. The data reflect roughly similar results with the use of verapamil and dipyridamole as enhancing agents, with markedly lower bioavailability achieved with progesterone.

FIG. 9 sets forth a graphical comparison between the concentration-time profile of paclitaxel determined for the group of rats administered verapamil (10 mg/kg) as an enhancing agent with the values determined in a prior study for animals administered oral paclitaxel (9 mg/kg) alone and another group administered oral cyclosporine (5 mg/kg) both one hour before and again together with a dose of oral paclitaxel (9 mg/kg). The group receiving cyclosporine achieved far higher blood levels than the other groups throughout almost the entire 24-hour period.

FIGS. 10 and 11 represent parallel graphical comparisons to FIG. 9, but with the values for the progesterone-administered group shown in FIG. 10 and the dipyridamole group shown in FIG. 11 in place of the verapamil group of FIG. 9.

EXAMPLE 5

Three groups of rats were administered, respectively, 100 mg/kg of verapamil orally, 5 mg/kg of megestrol acetate orally and 50 mg/kg of ketoconazole orally as enhancing agents, both alone and one hour later with an oral dose of radiolabeled paclitaxel. A graphical comparison of the whole blood concentration-time profile (measured as concentration equivalents versus time) determined for the three groups is set forth in FIG. 12. The data reflect roughly similar results for verapamil and megestrol acetate as enhancing agents, with markedly higher bioavailability achieved with ketoconazole in the first 12 hours.

FIG. 13 sets forth a graphical comparison between the concentration-time profile of radioactivity determined for the group of rats administered verapamil (100 mg/kg) as an enhancing agent with the values determined in a prior study for animals administered oral paclitaxel (9 mg/kg) alone and another group administered oral cyclosporine (5 mg/kg) both one hour before and again together with a dose of oral radiolabeled paclitaxel (9 mg/kg).

FIGS. 14 and 15 represent parallel graphical comparisons to FIG. 13, but with the values for the megestrol acetate-administered group shown in FIG. 14 and the ketoconazole group shown in FIG. 15 in place of the verapamil group of FIG. 13.

FIG. 16 sets forth graphical comparisons between the concentration-time profiles of radioactivity determined for the group of rats administered 10 mg/kg of verapamil in Example 4 and the group administered 100 mg/kg of verapamil in Example 5.

FIG. 17 sets forth graphical comparisons between the concentration-time profiles of radioactivity determined for the group of rats administered 5 mg/kg of progesterone in Example 4 and the group administered 5 mg/kg of megestrol acetate in Example 5.

In both FIGS. 16 and 17 there are also shown the same profiles reflected in FIGS. 13-15 for study groups receiving oral radiolabeled paclitaxel alone and oral radiolabeled paclitaxel together with and one hour after 5 mg/kg of cyclosporine.

The mean pharmacokinetic parameters for the study groups of animals discussed in Examples 4 and 5 are set forth in Table 6.³

The data generated by the studies of Examples 4 and 5 and reflected in Table 6 and FIGS. 8-17 clearly indicate the efficacy of cyclosporine as an oral bioavailability enhancing agent and its superiority to high or low dose verapamil, progesterone or megestrol acetate, particularly in the first 12 hours after paclitaxel dosing. They also indicate that ketoconazole, while not as effective as cyclosporine, also has significant activity in promoting the oral absorption of paclitaxel.

                                      TABLE 6                                      __________________________________________________________________________     Mean Pharmacokinetic Parameters For NP951202 and NP960101                      Study       Dose/Route                                                                              AUC0-24  t1/2                                                                               Cmax                                         Protocol                                                                            Treatment                                                                             (mg/kg)  (μg × hr/mL)                                                                F %                                                                               (hour)                                                                             (μg*eq/mL)                                __________________________________________________________________________     NP951001                                                                            Paclitaxel only                                                                       9/IV     32.04    20.15                                                                              37                                                Paclitaxel only                                                                       9/PO     3.24  10.1                                                                              18.86                                                                              0.21                                              Cyclosporin                                                                           5/PO(C), 12.02 37.5                                                                              14.51                                                                              0.82                                                     9/PO(P) 5/PO(C)                                                    NP951202                                                                            Verapamil                                                                             10/PO(V),                                                                               6.34  19.8                                                                              24.4                                                                               0.78                                                     9/PO(P) 10/PO(V)                                                        Progesterone                                                                          5/PO(Pro),                                                                              3.78  11.8                                                                              20.0                                                                               0.26                                                     9/PO(P) 5/PO(Pro)                                                       Dipyridamole                                                                          10/PO(D),                                                                               6.18  19.3                                                                              26.6                                                                               0.46                                                     9/PO(P) 10/PO(D)                                                   NP960101                                                                            *Verapamil                                                                            100/PO(V),                                                                              NA    NA NA  0.44                                              (animals died)                                                                        9/PO(P) 100/PO(V)                                                       Megace 5/PO(M), 5.19  16.2                                                                              23.1                                                                               0.44                                                     9/PO(P) 5/PO(M)                                                         Ketoconazole                                                                          50/PO(K),                                                                               8.03  25.1                                                                              9.23                                                                               0.69                                                     9/PO(P) 50/PO(K)                                                   __________________________________________________________________________

EXAMPLE 6

Three groups of three male rats each were fasted 16-18 hours prior to dosing. At the end of the fasting period one group of rats was administered an oral dose of 5 mg/kg of cyclosporine. One hour later, that group was administered 5 mg/kg of cyclosporine orally with 1 mg/kg of 3H-radiolabeled etoposide orally. The other two groups were administered after fasting only 1 mg/kg of 3H-etoposide IV and 1 mg/kg 3H-etoposide orally, respectively. The procedures for blood and urine collection and for determining total radioactivity were the same as in Examples 4 and 5 except that blood was taken at two additional intervals from the group receiving etoposide IV, at 0.033 and 0.25 hours. The resultant data are set forth in Table 7.

FIGS. 18 and 19 set forth graphically the mean whole blood concentration-time profile of etoposide determined for the three study groups. In FIG. 18 the ordinate scale runs from 0-1 etoposide concentration equivalents (ppm), while in FIG. 19 the ordinate scale runs from 0-0.2 etoposide equivalents (ppm) to more clearly illustrate the differences between the values achieved for the three groups.

The data set forth in Table 7 and FIGS. 18 and 19 demonstrate the efficacy of cyclosporine as an oral bioavailability enhancing agent for etoposide, particularly in the first 12 hours after dosing.

                                      TABLE 7                                      __________________________________________________________________________     Mean Pharmacokinetic Parameters For NP960102                                   Study      Dose/Route                                                                              AuC0-24                                                                              F  t1/2                                                                               Cmax                                          Protocol                                                                            Treatment                                                                            (mg/kg)  (μg × hr/mL)                                                                (%)                                                                               (hour)                                                                             (μg*eq/mL)                                 __________________________________________________________________________     NP96010                                                                        Grp A                                                                               Etoposide                                                                            1/IV     1.08     26.5                                                                               2.16                                               only                                                                      Grp B                                                                               Etoposide                                                                            1/PO     0.61  56.5                                                                              19.1                                                                               0.03                                               only                                                                      Grp C                                                                               CsA,  5/PO(C), 1.04  96.3                                                                              18.1                                                                               0.12                                               Etoposide +                                                                          1/PO(P) 5/PO(C)                                                          CsA                                                                       __________________________________________________________________________

EXAMPLE 7

An excretion balance study for paclitaxel in rats was conducted. Three groups of 4-5 male rats each were fasted 12-14 hours prior to dosing. At the end of the fasting period one group of rats was administered an oral dose of 5 mg/kg of cyclosporine. One hour later, that group was administered 5 mg/kg of cyclosporine orally with 9 mg/kg of radiolabeled paclitaxel orally. The other two groups were administered after fasting only 9 mg/kg of radiolabeled paclitaxel IV and 9 mg/kg of radiolabeled paclitaxel orally.

The urine and feces were collected from each animal at the following intervals: 0-2, 2-4, 4-8, 8-12, 12-24, 24-36, 36-48, 48-72, 72-96, 96-120, 120-144, and 144-168 hours post-dose. Tissue collection was performed at 168 hours post-dose. The procedure for determining total radioactivity was the same as in Examples 4 and 5.

FIG. 20 sets forth a graphical comparison of the mean cumulative percentage of dose of paclitaxel detected in the feces and urine of the test animals over the 168 hour period. The group of rats administered cyclosporine both before and with the oral paclitaxel exhibited a markedly lower percentage of dose in feces than the other two groups and a significantly higher percentage of dose in urine, indicating that substantially more of the oral paclitaxel diffused through the gut wall and entered the systemic circulation of the animals in the cyclosporine treated group. In addition, the fact that the percentage of dose in urine was significantly higher for the rats administered oral cyclosporine and paclitaxel in comparison with the IV-paclitaxel group indicates that the concomitant oral administration caused a higher concentration of radioactivity to pass through the genito-urinary tract.

FIGS. 21-24 are bar graphs reflecting the mean ppm values of paclitaxel detected in a variety of tissues harvested from the rats in the three study groups, Group A representing the animals administered paclitaxel IV, Group B representing those administered paclitaxel orally and Group C representing the cyclosporine-treated group. These graphs show that the levels of paclitaxel found in the various tissues from the rats in Group C were roughly comparable to the levels observed in the rats from Group A that received paclitaxel IV, except in the liver where the level of paclitaxel was more than twice as high in the cyclosporine treated group as in the group administered paclitaxel IV. The levels detected in the tissues of the rats of Group B (administered oral paclitaxel alone) were quite low, in most instances far less than half of the levels in either of the other groups.

The data resulting from this study are set forth in Tables 8 and 9.

                  TABLE 8                                                          ______________________________________                                         EXCRETION BALANCE STUDY FOR PACLITAXEL IN RAT                                  Radioactivity in Urine, Feces and Tissues Expressed as % of Dose               (Mean Values)                                                                  SAMPLE   GROUP A       GROUP B  GROUP C                                        ______________________________________                                         Urine    9.160         6.660    18.350                                         Feces    79.660        84.410   61.250                                         Tissues  1.710         0.600    1.430                                          Total    90.530        91.670   81.030                                         ______________________________________                                    

                  TABLE 9                                                          ______________________________________                                         EXCRETION BALANCE STUDY FOR PACLITAXEL IN RAT                                  Radioactive Residues in Tissues Expressed as PPM (Mean Values)                 SAMPLE    GROUP A      GROUP B  GROUP C                                        ______________________________________                                         Brain     0.101        0.029    0.096                                          Heart     0.085        0.025    0.088                                          Lung      0.143        0.030    0.136                                          Liver     0.237        0.074    0.566                                          Kidney    0.180        0.032    0.119                                          Muscle    0.079        0.025    0.080                                          GI Tract  0.083        0.021    0.055                                          Testes    0.346        0.037    0.217                                          Pancreas  0.078        0.018    0.080                                          Carcass   0.143        0.053    0.099                                          Bone      0.035        0.007    0.034                                          Spleen    0.101        0.024    0.083                                          Prostate  0.081        0.022    0.090                                          S. Vesicles                                                                              0.121        0.024    0.094                                          Blood     0.112        0.034    0.106                                          Plasma    0.126        0.038    0.124                                          ______________________________________                                    

EXAMPLE 8

The procedure of Examples 4 and 5 was followed, but the three groups of three male rats each were orally administered respectively 5 mg/kg doses of cyclosporin D, cyclosporin G and cyclosporin A, both alone and one hour later together with an oral dose of 9 mg/kg radiolabeled paclitaxel. FIG. 25 sets forth a graphical comparison of the whole blood concentration-time profiles for radioactivity determined in these three test groups. While all three cyclosporins showed substantial activity in promoting oral absorption of paclitaxel, the cyclosporin D, which has the least immunosuppressive activity of the three cyclosporins tested, exhibited the greatest bioavailability enhancing activity.

EXAMPLE 9

The procedure of Examples 4 and 5 was followed, but the three groups of three male rats each were orally administered respectively a 5 mg/kg dose of cyclosporin A, 50 mg/kg ketoconazole and 5 mg/kg cyclosporin A plus 50 mg/kg ketoconazole, both alone and one hour later together with an oral dose of 9 mg/kg radiolabeled paclitaxel. A graphical comparison of the results achieved is set forth in FIG. 26. The group receiving the combination of ketoconazole and cyclosporin A unexpectedly exhibited significantly higher blood radioactivity levels over almost the entire 24-hour period than the groups receiving only one of these enhancing agents.

EXAMPLE 10

The procedure of Examples 4 and 5 was followed, but the three groups of three male rats each were orally administered respectively a 100 mg/kg dose of captopril both alone and two hours later together with an oral dose of 9 mg/kg radiolabeled paclitaxel, a 5 mg/kg dose of cyclosporine alone and again one hour later together with a 9 mg/kg oral dose of radiolabeled paclitaxel, and a 9 mg/kg oral dose of radiolabeled paclitaxel alone. A graphical comparison of the results achieved is set forth in FIG. 27.

The aforedescribed studies produced several previously unknown and unexpected findings which are all of great significance to the clinical management of many diseases, particularly various types of cancer:

1. MDR (P-glycoprotein) inhibitors can be administered orally to effectively enhance the oral bioavailability of treatment agents which have until now been administered only parenterally because therapeutic blood levels cannot be attained upon oral administration.

2. Co-administration of oral MDR inhibitors with target drugs having poor oral bioavailability can achieve sustained blood levels of the target drugs comparable to that achieved with IV infusion therapy but with a less abrupt initial rise in blood levels and hence less likelihood of toxic side effects.

3. The oral co-administration of MDR inhibitors and target drugs increases the proportionate concentration of the target agent in the liver in comparison with IV administration, making the novel method of administration particularly useful in the treatment of liver tumors and metastases.

4. Administering MDR inhibitors orally prior to administration of concomitant oral doses of MDR-inhibiting enhancing agent and target drug increases the oral bioavailability of target drugs to a significantly higher degree than co-administration of the enhancing and target agents with no preadministration of enhancing agent.

5. Cyclosporins, particularly cyclosporins A and D, are much more effective agents for enhancing the bioavailability of antitumor agents than other MDR inhibitors such as verapamil and progesterone. Ketoconazole has clinically significant oral bioavailability-enhancing activity, but less than the cyclosporins.

In general, the various aspects of the invention enable and make practical for the first time the administration of oral dosage forms of widely used pharmaceutical agents, particularly anti-cancer drugs such as paclitaxel and etoposide, which until now could only be administered effectively or reliably by IV infusion. The use of such oral dosage forms in the clinical management of cancers will promote patient comfort, convenience and compliance and result in cost savings to patients, hospitals and government and private medical insurers.

In addition, the teachings of the invention set forth herein provide information regarding the selection of target and enhancing agents as well as timing, schedules and dosing. This information and the methods and compositions of the invention provide clinicians with procedures for sustaining therapeutic levels of drugs which require narrow windows of drug concentrations while avoiding unnecessary and frequently harmful peaks and valleys in blood concentration levels.

Although the invention in its various aspects pertains principally to the use of MDR inhibiting agents to enhance the oral bioavailability of drugs which experience multi-drug resistance as a result of the P-glycoprotein encoded by the MDR1 gene, there is another gene which has recently been found to confer a multi-drug resistance phenotype in certain laboratory systems: the gene for multi-drug-resistance-associated protein, MRP (e.g., Zaman et al., Proc. Natl. Acad. Sci. USA, 91: 8822-8826, 1994).

Less is known about this new gene and its protein product, a 190-kd membrane bound glycoprotein. Although both the MRP and MDR1 genes encode membrane glycoproteins that can act as transporters of multiple drugs, there are differences in function, likely substrates, and prognostic significance between these two genes. For example MRP but not MDR1 gene expression is a good marker of poor clinical outcome in patients with neuroblastomas. The putative function of the MRP-related proteins is to serve as an efflux pump for glutathione S-conjugates. Thus, molecules that undergo glutathione conjugation would be susceptible to the action of the MRP-related system.

The oral bioavailability of pharmacologically active agents (or exposure of the tumor to such agents) which are subject to resistance by MRP-related proteins can be enhanced by orally co-administrating MRP inhibitors. As with the MDR inhibitors, the preferred embodiment of this method of increasing oral bioavailability is the oral administration of one or more MRP inhibitors prior to the oral co-administration of one or more MRP inhibitors and one or more target agents subject to MRP-related resistance.

Examples of target agents of this type include (but are not limited to) vinca alkaloids (e.g., vincristine), anthracyclines, epidophyllotoxins (e.g., etoposide) and various taxanes. Examples of MRP inhibitors that can increase oral bioavailability of target agents include, but are not limited to, cyclosporins, ketoconazole, captopril and the experimental drugs VX-710 and VX-853 (Vertex Pharmaceuticals, Inc., Cambridge, Mass.). The structures of VX-710 and VX 853, as well as many related compounds, are disclosed in U.S. Pat. No. 5,192,773.

Another method of improving the oral bioavailability of agents subject to MRP-related resistance is to co-administer with those agents glutathione or substances which form glutathione-conjugated products which would interfere with the functioning of the MRP system and enhance the absorption of the target agents from the gut, or increase the systemic exposure of agents subjected to MRP-related transport.

Yet another system capable of conferring multi-drug resistance is the so-called Lung Resistance-Related Protein (LRP), because it was first identified in a multi-drug resistant lung cancer cell line. This protein is the major structural protein of the so-called vault apparatus, a large abundant cytoplasmic ribonucleoprotein particle, which has been conserved from slime mold to man. Inhibition of this system may also positively affect oral bioavailability of certain agents. LRP is found in highest expression in epithelial cells with secretory and excretory functions, as well as in cells chronically exposed to xenobiotics, such as bronchial and intestinal lining cells (Scheffer et al., Nature Medicine, 1: 578-582, 1955). Therefore, this system could also serve as a target for enhancing oral bioavailability.

It has thus been shown that there are provided methods, compositions and kits which achieve the various objects of the invention and which are well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiments set forth above, it is to be understood that all matters herein described are to be interpreted as illustrative and not in a limiting sense. 

What is claimed as new and desired to be protected by Letters Patent is set forth in the following claims:
 1. A method of increasing the bioavailability upon oral administration to a mammalian patient of a pharmacologically active target agent, said method comprising the oral administration to the patient of an effective amount of said target agent and an oral bioavailability-enhancing effective amount of a cyclosporin bioavailability-enhancing agent, said target agent being selected from the group consisting of paclitaxel and pharmaceutically acceptable salts thereof.
 2. A method according to claim 1 wherein the enhancing agent is administered eithera) about 0.5-24 hrs. before, or b) less than 0.5 hr. before, together with or less than 0.5 hr. after, or c) both about 0.5-24 hrs. before and again less than 0.5 hr. before, together with or less than 0.5 hr. after, the administration of the target agent.
 3. A method according to claim 1 wherein the patient is a human patient.
 4. A method according to claim 1 wherein the target agent and the enhancing agent are each administered in separate oral dosage forms.
 5. A method according to claim 1 wherein the target agent and the enhancing agent are administered together in a combination oral dosage form.
 6. A method according to claims 4 or 5 wherein the target agent is paclitaxel.
 7. A method according to claim 1 wherein the enhancing agent is a cyclosporin selected from the group consisting of cyclosporins A through Z and (Me-Ile-4)-cyclosporin.
 8. A method according to claim 7 wherein the cyclosporin is cyclosporin A, cyclosporin D or cyclosporin G.
 9. A method according to claim 2 wherein the enhancing agent is administered both about 0.5-24 hrs. before and again less than 0.5 hr. before, together with or less than 0.5 hr. after the administration of the target agent.
 10. A method according to claim 2 wherein two or more doses of the target agent are administered after a single dose of the enhancing agent.
 11. A method according to claims 1, 4 or 5 wherein the effective amount of the target agent is about 20-600 mg/m² based on patient body surface area.
 12. A method according to claim 11 wherein the target agent is paclitaxel.
 13. A method according to claims 1, 4 or 5 wherein the effective amount of the enhancing agent is about 0.1 to about 15 mg/kg based on patient body weight.
 14. A method according to claim 13 wherein the enhancing agent is cyclosporin A.
 15. A method according to claim 14 wherein the enhancing agent comprises about 5 mg/kg of cyclosporin A.
 16. A method according to claim 1, 4 or 5 wherein the target agent comprises about 20-600 mg/m² of paclitaxel and the enhancing agent comprises about 0.1 to about 15 mg/kg of cyclosporin A.
 17. A method according to claims 1, 4 or 5 wherein the target agent dosage form, the enhancing agent dosage form or the combination dosage form is each selected from the group consisting of tablets, capsules, caplets, pills, lozenges and liquid solutions, suspensions or elixirs.
 18. A method according to claim 17 wherein the target agent dosage form or the combination dosage form comprises paclitaxel and a polyethoxylated castor oil.
 19. A method of treating a mammalian patient afflicted with a disease responsive to a pharmacologically active target agent comprising the oral co-administration to the patient of an effective amount of the target agent and an oral bioavailability-enhancing effective amount of a cyclosporin bioavailability-enhancing agent, said target agent being selected from the group consisting of paclitaxel and pharmaceutically acceptable salts thereof.
 20. A method according to claim 19 wherein the disease is a cancer, tumor or neoplastic growth.
 21. A method according to claim 19 wherein the disease is selected from the group consisting of ovarian cancer, breast cancer, lung cancer, head and neck carcinomas, hepatocellular carcinoma, liver metastases, genito-urinary tract cancers, polycystic kidney disease and malaria.
 22. A method according to claim 19 wherein the enhancing agent is administered eithera) about 0.5-24 hrs. before, or b) less than 0.5 hr. before, together with or less than 0.5 hr. after, or c) both about 0.5-24 hrs. before and again less than 0.5 hr. before, together with or less than 0.5 hr. after, the administration of the target agent.
 23. A method according to claim 22 wherein the enhancing agent is administered both about 0.5-24 hrs. before and again less than 0.5 hr. before, together with or less than 0.5 hr. after the administration of the target agent.
 24. A method according to claim 19 wherein the target agent and enhancing agent are each administered in separate oral dosage forms.
 25. A method according to claim 19 wherein the target agent and the enhancing agent are administered together in a combination oral dosage form.
 26. A method according to claims 19, 24 or 25 wherein the target agent is paclitaxel.
 27. A method according to claims 19, 24 or 25 wherein the enhancing agent is a cyclosporin selected from the group consisting of cyclosporins A through Z and (Me-Ile-4)-cyclosporin.
 28. A method according to claim 27 wherein the cyclosporin is cyclosporin A, cyclosporin D or cyclosporin G.
 29. A method according to claims 19, 24 or 25 wherein the effective amount of the target agent is about 20-600 mg/m² based on patient body surface area.
 30. A method according to claim 29 wherein the target agent is paclitaxel.
 31. A method according to claim 30 wherein the target agent comprises about 2-9 mg/kg of paclitaxel based on patient body weight.
 32. A method according to claims 19, 24 or 25 wherein the effective amount of the enhancing agent is about 0.1 to about 15 mg/kg based on patient body weight.
 33. A method according to claim 32 wherein the enhancing agent is cyclosporin A.
 34. A method according to claim 33 wherein the enhancing agent comprises about 5 mg/kg of cyclosporin A.
 35. A method according to claims 19, 24 or 25 wherein the target agent comprises about 20-600 mg/m² of paclitaxel based on patient body surface area and the enhancing agent comprises about 0.1 to about 15 mg/kg of cyclosporin A, cyclosporin D or cyclosporin G based on patient body weight.
 36. A method of treating a mammalian patient suffering from liver cancer by orally administering to the patient an effective amount of a target agent selected from the group consisting of paclitaxel and pharmaceutically acceptable salts thereof in a manner which creates a higher initial local concentration of the target agent in the patient's liver than the initial concentration in the general systemic circulation or in other organs, said target agent being co-administered to the patient with an oral bioavailability-enhancing effective amount of a bioavailability-enhancing agent selected from the group consisting of cyclosporins A-Z and (Me-Ile-4)-cyclosporin.
 37. A method according to claim 36 wherein the enhancing agent is cyclosporin A, cyclosporin D or cyclosporin G.
 38. A method according to claim 36 wherein the enhancing agent is administered eithera) about 0.5-24 hrs. before, or b) less than 0.5 hr. before, together with or less than 0.5 hr. after, or c) both about 0.5-24 hrs. before and again less than 0.5 hr. before, together with or less than 0.5 hr. after, the administration of the target agent.
 39. A method according to claim 38 wherein two or more doses of the target agent are administered after a single dose of the enhancing agent.
 40. A method according to claims 1, 19 or 36 wherein the target agent is paclitaxel and the enhancing agent is cyclosporin A. 